Thin-walled tubing for use as electrode structures of electron discharge devices



Sept. 9. 1952 GARNER r 2,610,304

THIN-WALLED TUBING FOR USE AS ELECTRODE STRUCTURES OF ELECTRON DISCHARGEDEVICES Filed March 31, 1948 3 Sheets-Sheetl 1 f i i Ll/71AM Hg {1W Mum.WW

#ZI'IM M Zmventor L] d B Garner Z Z Wi'Z am M Parker 4 C(itorneg Sept.9. 1952 P. GARNER ET AL 2,610,304

THIN-WALLED TUBING FOR USE AS ELECTRODE STRUCTURES OF ELECTRON DISCHARGEnsvxcas 5 Sheets-Sheet 2 Filed March 51, 1948 Zhwentor .LZOljd f. arner& W M11282 M Parker Sept 9. 1 1.. P. GARNER ET AL 2,610,304

THIN-WALLED TUBING FOR usE AS ELECTRODE STRUCTURES OF ELECTRON DISCHARGEDEVICES Filed March 31, 1948 5 Sheets-Sheet 3 7 lnvemor L10 d I. Garner43 WWi/Z'am ZParker v Gttomeg through a -;'SIna11 Patented Sept. 9, 1952CHARGE DEVICES fIil'oyd'P. Garnerand William N. Parker, Lancas- "trgPaassignors to Radio Corporation of Amerioa; a-corporation of; DelawareApplication March 31 Ellen-resent inYentionreIa-tes to articles madehy-. a...novel-.methiod of .coldworking of ductile materials intoga'hodyor geometric. shape haying. aioildikew all. thickness. andhaving a.cross-sectionalarea. so. thin.that,..present methodsofjco-ldworking.meta1s;.l;are impractical of. application.

novel .methcidoi coldworking .meterials isclaimedour.idivisionalapplication. Serial No- 210,095,;filed.. E-ebruary.En'.l95-2, .;and ..ass 'igned t the.- sameLJassignee-as'. themresentapplication :As welliunelerstoolluby' those skilled in. ,the prior.:art, cold-working of...metals takes place at temperatures below the.reorystallation. temperature oi the metal. andre uires stresses beyondthe. elastioli-mitin order; to. secure the desired pennanent-plastiedeformations. .,With. a. cQmon metals the/necessary stressesareoi considerahlesmag-nitudeand may heat the order nf one hundred-thousand pounds.pergsquare inch,

j so: that-even. ioriparts, .of. relatively. small areas.

enormous ;g-total- ,.pressuresware required if the whole area .or fthfiwork blank is cold. .worked vsimultaneously; v

'Eypieal-examples. of such.cold-working..pro.casses are: .axi-alrolling, extrusion... spinning, and

the like. Each oi-theserprooesses isinherently objectionable when theductile. materialsare; to beueduced lt very thin dimensions. bycold-work.- ing. .In;=.theaca;se of extrusion oraxial rollingvhrooesses;:the:pr-tessures. required for plastic deformation or theworkqmateriai-are extremely high.

.Thewoomparativelyrsmall reduction in. thicknesswof:the'plankiin theoaseo-f axial rollin accomplished byarsingle- :pass of. the materialthmuehrthe rolling apparatus is: such that .a number: of--pas-ses-.-therethrough .is. necessary to obtain .the' desiredultimatethickness. Further moresrroll'ing: equipment, becomes verymassive, whererhlgh pressures-are required. .Incr-der to alloldj theneoessitywoihighpressures. the luse of smallsdiameterrrollshas 'ibeen.resorted :to. but toinreventsserlousrbending ofgthe rolls it; isnecessary toisupportieadhuof .thertwo working rolls aux rollers. portedhyianother jgroup of .-auxillary.-rollers;and so-aonzuntils-sufiJ-cient' rigidity is: seeured. :JIh-e struoture .oi-suchya clustermill requires conslm arable Y costly: development, and the amount ofreduction in thickness per pass through-the 3130115 is limited-by.thedriving torque-available. .Since all athedriving torque must betransmitted 'diameter roll, the. 'aivailahle is small. As .a" .result,.la great. many passeseareusuallyareguired. to prqduce the; {thin I LThese. in turn. are sup:

194.8, Setial.No..18, l.1& 3 Claims. (cram-43) metal foil required.Since each work pass har ens the materiaL. frequent annealing pneratinnsre r q i d. .the whol v prooessh comes' edious, and the resultsgenerally.unsatisfactory- Also, a rolling. mill. unsuited tothefzormingof parts where only a predetermined portion is to be reduced inthickness.

By extrusion methods commonly used hydrau lie pressure is built up.simultaneously .mvith entire volume of metal which is being extruded.Not only mus the total appliedforces be. lar but largestrone tools.mustbeused to. constrain the metal like afluid. a. ylinder. .Theresultis that aside from using great pressures, which complicates, theequipment. prior art. methods arelthus unsuitable at .praotieine ourmethod.

In spinning, amoderatelythin. metalhlank is rotated,..agai.n.s:t .around. nosed tool. or roller which is'mani ulatedto force the metalagainst a. form or mandrelwhich rotates with the work.

Only a slight reduction in .thiekrresstakes .place each timethe toolispassedover the worlg. 'lj-he attainment of very. thin. wallthicknesses by repeated spinning diificult for two reasons: First, the sinning .of, the metal cau es considerable work hardening that annealingis. required after a relatively small reduction in thickness. Repeatedheating. and handlin of deli-cateparts is apt tote disas rous. :Secondm,as-the. wall heoomesvery thini it cannottransmit. the. forces requiredby the spinningprocess and-serious; buckling and/or fraeture-results. ispr marily due to -the fact sthat,,in reducing wall thickness byspinning, the tool is ordiniari y moved toward. unworkedv material,andiaway irom the driving force. In. this way-thae-thHl-WOTK hardenedmetal must transmit the necessary driving forces, which necessarilymust'belimitecl by the strength of. the. thin material.

It-will thus beseen thatathere does-not exist in the prior artasuitablemethodrof mechanicaly accomplish ng by ccM-wrkineof ductile meals great reductions in wall: thickness without; the use of largedriving; forces, massivermach nery, and/or frequent annealing;especially when lo like wall thioknessesare required. I

The source of these difileulties. i-s-removedhy novel method ofcold-working metal and an paratus for carryingoutthe, method. ,Themethod may be classed as anextrusion-scannine pm ess,-whichdifferentiates basically from conventionalextrusion methods of the.priorart ha i t invblves what we .nhOclse. to calla scanning? lea life,and. the. design f' he apparatus is. such 0' tiliaeth si' ea ur mer ellure ucin wall thickness of a work blank, which may, for

example, comprise a length of tubing the wall of which is greatlyreduced by a single pass of the tubing through the apparatus. The tubingitself rnay be so manipulated in its passage through theextrusion-scanning apparatus as to provide a part or shape, which may bea very thin walled cylindrical tube capable of use as such or furtherfabricated into an electrode, such as a grid, useful in electrondischarge and other devices, which part has greatly enhanced electronic,mechanical, thermal and/or electrical properties and is capable ofeconomical mass production.

An object of the present invention is the provision of an electrode partor other article of manufacture having novel characteristics, bothmechanical and electrical, advantageous to the use of said part in anelectron discharge and like devices.

Other objects, advantages and results of the invention will manifestthemselves from a reading of the following description in connectionwith the accompanying drawings.

Referring to the accompanying drawings:

Figure 1 is an elevation, partly in section, of

one form of apparatus for producing the invention;

Figure 2 is a section taken on lines 2-2 of Figure 1;

Figure 3 is an enlarged cross-section taken through the axis of acylindrical mandrel and a tubular work piece, showing the wall thinningoperation; 7 V

Figure 4 is an elevation of an elongated tubular work piece along whichthe thinning operation has been repeated several times;

Figure 5 is an enlarged sectional view of a cathode structure utilizingone of the thinned end products embodying the invention as a support forthe cathode;

Figure 6 is an enlarged fragmentary sectional view illustrating onephase of the operation;

Figure '7 is an enlarged elevation, partly in section, and similartoFigure 3, showing details of processing awork piece;

Figure 8 is an enlarged fragmentary cross-section, on lines 8--8, ofFigure'7, showing the extrusion scanning region or volume incompletelybounded in configuration;

Figure 9 is a schematic illustration showing the helical path defined inone form of practicing the process; 7

Figure 10 is a sectional view showing the flow of the work underexcessive back pressure by the working tool having a peripheral head andan adjacent flat surface;

Figure 11 is a view similar to Figure 10, except that the Working toolhas only a bead in forcible contact with the Work;

Figure 12 is a sectional view of another form or the working tool whichis provided with a rotatable rounded nose portion; and

Figure 13 is a section, partly schematic, of a modified form ofapparatus, wherein a reciprocating motion is substituted for a principalrotary motion employed in the apparatus of Figure 1.

The present invention, described in its elemental concepts, is directedto articles made by 4 extrusion-scanning process is characterized by thenovel features of scanning that portion of the work blank undergoingdeformation and having the co-ordinated components or forces involvedapplied at any instant to a relatively limited geometric volume of thework.

The meaningof the term scanning as applied to our extrusion process willbe hereinafter defined, as well as certain other terms which we mayemploy in a somewhat unconventional manner, but the intended meaningwill be obvious and fully supported by the description of the inventiontaken in connection with the drawings.

In one form of practicing our process, a piece of tubing may be placedon a smooth cylindrical mandrel, which provides a hard backing surface,and the-sheathed mandrel is passed through a system of rollers. Thearrangement, design and manipulation of the rollers comprising thissystem are adjustable with respect to the work, but the rollers areadapted to be kept at a fixed radial separation from the mandrel whichdetermines the ultimate final thickness of the completed tube. One endof the tube is constrained and fixedly secured to the mandrel and theother end is free to move axially thereof. As the tube is reduced inthickness the heavy or thick walled portion is used to force the thinnedwall portion through and beyond the rollers. Means are provided forradially adjusting the rollers relative to the axis of the mandrel andsimultaneously applying localized pressure through the rollersperpendicular to each successive portion or'region of the tubing beingworked in its advance through the roller system. Each roller is providedwith a beadof small radius relative to the diameter of the roller. Thisconstruction permits relatively small applied total forces to accomplishgreat reduction in wall thickness or the tubing by virtue of theredistributing and'intensifying action of small mutual contact areasbetween the work part and the roller beads.

As explained hereinafter, an extrusion scanning aperture is formed ateach roller as it is brought into contact with the opposing surface of arotating tubular work blank.

A driving force is applied to the tubing in a direction parallel to theaxis of rotation and towards the extrusion aperture. This force providesthe axial component required in the execution of our extrusion-scanningprocess as applied in the present illustration. 7

By adjusting the rollers, changing the surface of the mandrel, andsimilar expedientaa variationin the end products may be obtained.

For example, by forming depressions in the outer.

surface of the mandrel and applying a force in a radial direction to"the work material, there can be produced a flow of metal into thedepressions formed in the mandrel, thus providing thicker longitudinalsections corresponding to the contour of the mandrel depressions. Such amodification is disclosed in co-pending application filed by William N.Parker-Serial Number 84,406, filed March 30, 1949, now Patent No.2,565,623,;issued August 28, 1951, relating to a'grid structure and thelike. However, in the present application a smooth mandrel is used, andthe resulting product may be an electrode element hereinafter describedmore specifically.

The process herein disclosed contemplates, and the apparatusillustratedfor practicing the same provides means for imparting threeprincipal forces to the work through the portion thereof to be worked:one rotating the tube,- another process. it'isfdeemedEadvisableFthatcerta I employee by us tepr s nnyden eu tna tlicf 5. 1310311118thejubeparallelto the axispf the sup-. h rtinermandreinanctithethirdapplying-pressure pernendiculartothersurface'oi" the-work.

'"Ihe:proce ss-may-besaid-w embody: three "characteristic on outstandingfeatures: "(1 -thaprocessis aiormof extrusion-embodying at leasttwoscanning motions; (2) only a local asymmetrical" geometric volume :ofmaterial .is worked: at a time and i631. the extrusion is completed in asingle; passage-of the material undergoing processing, arrangement:avoids objectionable stresses strains which are :encountered' in atrial"rolling; spinning, .Jjdrawi'ng; and "similar metal workingpperationsemployed" heretotore.

agpreliminary to the "disclosure:oi-fiourt-inventi'om :the theory and/orf technique involved Inayrhe' explained by again: referringtotheEprior'art-relating to general ,extrusion' processes. com.- monlxpracticediandthenproceeding ,to. describe in. what ;1respect :;our rmethod. differstherefrom.v

The welt-known basic. extrusion; principle ;involyes; piacing;a.;pieceQ1: quantity-of ductile .material; in; somef form; of. aconstrainingdevice," so. that:.a piston actingiin. response to aiiorce. sets'-up;-;a;compressionthroughout the..materi a1; sumcientto cause plastic"flow 'thereofthroughgan orificeor diehaving. a contour incrosssectional area-substantially identical With.'that of thedesircd;:.extruded;product. pointed out. above to extrud'e the. metals-alarge hydraulic; pressure isscreated'finfthe entire volume oizthevmetal, withgattendant.'difficulties'causect thereby. p

' Tozavoid' ithese. "di'mculties, .we use: a; mechanism'wher'eby':hydrostatic gpr'essure sufiicient tor eidimsioxrlis' limited to acomparative ly;restricted;

geometric" volume V ofi the material being gproceased; This. differencein; principle is possiblez-byprodiming ascanningfi eifect'accomplisheo'byl emplaying; an" apparatus including -a--"roiler system responsiveto? coeordinated .iorcesyas moreiully describedLhereinafieri'..-:S'uflice it to say atthis.

' point:- that each,o1"- the: rollers-constitutes-partofiarretrectiyaextmsion scanningapertureg and by having one endr-of? the'work blank free to moveiaxialiy' of a"supporting-memberrsuch-asa,

mandrel'fthe reduced thinned portion--of:"the

worlciiiowsfreely longitudinaliy of the mandrel andin the saxncdirection: the motion of the unworlsedjr portion of, theblank which -rismoved axi'ally-z-againsttther rollers fbythe driving" source.

ili'he '-'-1ocalization -of*-th t'vorking '-"-fo'rce to "a restrictedvolume" while the a'xial' compressional forces are "transmitted'entirelythrough-the; portion tobe worked is; a distinguishing characteristicof-our process over ptior- 'art extrusion processew and '--makes "thaapplication of our extrusion method -practicar i'n reduc-ingWhewallthickness of" the work blanlcto 1001 of an. inch or less.Furthermorej-tha reductionnn wall thickness may-easilyhe atleasir'thirtyftimes' less than 'thep-original-wall thickness of thetubing,

the 'reduction fleeing accomplished in a I single pass; otthe blankthroughth'e-app a-ratnsi fiithougl'i themain steps' in our BXtIUSiQIY-pYOO -essreinai'n the samegva-riations imthe: apparatusproduction offdi'fierent end products. 7 The degree or VQHEtiOflinzapparatus wili depend up'onith'e. nature of the end product, andseveral such modifications res'ultii-rg from practicing the -hasicprocess-"herein dlsclosed constitute the basis 'forseparate-applications; v v Y significance thereof vvillggiveqa betterappreciationr ofourxprccessr-as theidescripticn proceeds.

.are :coordinated :bllli -capab1e of independent action,. and7preferah1YQQmgIeting the scanning in .a singl'e passage Oi "the-work-blank through the aperture. i511: 'mayIbe-noted" that the scanningtakesjplace injtherworls "undergoingrprocessing assitiisi. subiectediito"a rotationalyaxid/or transwersermovement relative :hetween the workmate'ri'atand. tool; with the result that-the movement ofi the work? isin an orderly path,i'which path must be resolvable into: at leasttwocorrelated: and mutually perpendicular directional components; forexample; longitudimlandtransverse, circiunierentiarandsradial, orcircumferentialandaxial. "mother words jthecornponents oflthe treatment;are or two -dimensions or dimotions and; become'efiective-in adjacent orcontinuous sequences.

The .term faperture as used? herein *withxrespecti to; our extrusionmethodmay be defined generally: as, constituting incompletely.boundeidropening which continuously scans-"through I the work :in.aziregiiialvsmooth, overlapping; and

nonerepeatingr path. In" this; respect our extrusion apertureldoesnothaye 1 a :closed surface contour which maybe characterized asavisually'identifiable static entity, such as .thedieaper- 'ture. .used.in conventional .formsriof extrusion whereinithe. .openingorzspace isbounded. by a continuous surface ;or surfaces sensually perceivable.:nather; it will be; appreciated that the term".extrusionaperture as.used herein'does .notrefer to, .or. identify,- a simple coexistentphysical. entity. of :bounded: surface with obvious shapeandidimensionbut. as constitutinsa shape determinedrby; theelementswhich are functionally relatedto eifectively'form an extrusion. opening through which. theextruded, portion of; the work. blankis; bcingliorced at any instantduring the. extrusionprocess. JItmay therefore be regarded, .-.asconsisting. of. several effective constraining. boundariesiwhichiinclude the. backing sur-iace. ormandrlel. .a worl; contactingsurface,

suchasarollerorothcit tool, and the adjacent portion. 'oiithe work;itselt,

.In. our. use. or. the. term .fintegraI we have in mindsparticularly.a.-. structure composedof one ;.piece. of. material-whichinay be givenvarious shapes but. all .of .such shapes. forming. a single body. iree..01 Joints Referring. tothedrawings, particularly Fi uresLto-Bgapparatus. for practicing the processmay a comprise a machinetool-similar. to a drill press.

Since these tools are.-well. .k.onwn,- onlythe parts essential toangunderstanding of. the. invention arezzshow-n. A: rotating: shaft;.32,isv carried by. a sleeve .3rwhich is mwableup-and down byoperationof a handleizby meansota gear 4. and arack 3T. JA maridrelirhasicloselyiitting hearings l0 in a y'okefifi which is?. in-turn.attachedi toa; base. 1'. "The base-'1' in-tum-restsona*'drillr.press.:table B wh'ich isconnected=mechanically to the upperpart of the press The base 'l'supports the tube reducing device havingan auxiliary frame 9 loosely fitting within the yoke 6. .Thecloselyfitting bearings I and yoke 6 serve to keep the mandrel running trueabout its axis and substantially perpendicular to the. upper surface ofthe base I.- The frame 9 carries non-adjustable rollers II and I2, .and1- adjustable roller l3 mounted in slide block I4 slidablewithin frame 9toward and away from'rollers, H. and I2 (see Figure 2).

That is to say, the rollers II and I2 .altho ugh rotatable are of astationary axis type, i. e., nonadjustable relative to each other, beingmounted in the outer frame 9, while the roller I3 ,is mounted on theslide, and hence,v is adjustable with respect to the other rollers. For,the present illustration the rollers II, I2 and I3 may be 1 inch indiameter with a half round bead or ridge I5 havinga radius of .062 inch.This radius is notcritical but thereis usually an optimum for a givencombination of work metal, or thickness, and the amount of reduction,desired. .A general ratio of head radius to original wall thickness ofwork blank .may vary. between .1 and 10 depending on.the original wallthick.- ness, the material and the results desired. It is also to beunderstood that a wide'variety of shapes and/or cross-sections ofrollers may be employed. v

The auxiliary frame consisting of elements 9, I4, 33, 34, 35, 36 androllers II, I2 and I3 is free to slide on the base I so as to;automatically center the rollers about the work piece or tubing,referred to generally by the numeral ,I, and the mandrel 5. While theuse of three rollers is preferred on account of the inherent automaticcenhaving teeth 21. n; this instahce, his estate; has an outer smooth.surface. {If theiclosedend shaft 32 and the axial motion of the sleeve 3tering feature it is tobe understood that any number of rollers may beused in a suitable hold ing construction. v

Certain of the parts just described areshown more clearly in Figure 3wherein the work part I, having a thinned wall section I! and an un--worked end section I6 which may beclosed at one end, is fitted over themandrel 5. The end section I6 need not bea part of the tube I in orderto practice the process in its elemental form, that is, byv extrusionscanning, but for purposes of illustration .it is shown .for reasonsthat will'be obvious hereinaften. .Tlie wall thickness of the metal.tube I is reducedby the simultaneous application of axial pressure alongthe lines 13 and I9 (see arrows of Figure 3) andradial pressure 20,while the tube is being rotated under the rollers. The mandrel 5 servesto back up the inner surface of the tube I in the region opposite therollers, and to transmit the necessary rotational torque 2| to the workpiece through clamp=-' ing devices which may comprise a collar 22provided with a set screw 23. The relatively small radius bead I5 onrollers II, I2, and I'3 provides intense local pressure in region. ofthe portion 25 of tube I to be worked, causing plastic deformationandconsequent thinning down of the thick wall of the tube. The resultantthin pall portion I'I flows freely away from rollers I I, I2 and I3 andalongthe'mandrel 5with substantially no loss in volume of material. As aresult the length of the thin portion I! will be extended axially inproportion to the reduction in wall thickness. All three rollers II, I2and: I3 turn on precision needle bearings 25, as shownparticularly inFigures 1' and'2! As' illustrated'in Figure l,- the work partundergoing-treatment is a tube blank and it. is caused to rotate byt-aclutch sleeve 28 attached to the mandrel 5 and and shaft 32 withoutvibration or eccentricity, so that the mandrel 5 runs true with respectto the rollers II, I2 and I3. Any other suitable arrangement may beused. f

The, forming. operation combines the advantages of small.radius contact.surfaces and high unit pressure'of the cluster tyjpe rolling machinewith. the principal advantage of'an extrusion process in that thenecessary forces are transmitted by the relatively heavy Qunworked wall25 of the work piece I. The rollers II, ,I2' and I3 are preferably madeof hardened steel carefully formed and polished. It has been found thatthe hardness of the rollers should measure about 64 Rockwell C. whilethe hardness of the.

mandrel should measure between 64 to 66 Rockwell C. 7

.With the work piece I, mandrel 5 and associated parts 28, 3I and 32 allrotating as incheated by the arrow 2I at a speed of about 700'revolutions per minute, f'eed'screw33 is advanced by means of knurledhandle 34.- This causes slide I4 and roller I3 to move toward work pieceI and rollers .II and I2 and force the heads I5 of rollers I I, I2, andI3 into thework piece apredetermined. depth as set by nut 35'and locknut36K.

This depth is so chosen as to give the desired wall thickness of thinneddown portion [1. Handle 2 is now operated so that the attached gear 4andassociated rack3'l of the drill press exert a downward axial force ISon workpiece. I through elements .5, 28, 3| and 3:2;-.simultaneously thefriction between the work. piece I and. the mandrel 5 causes them to bedriven in unison and provides drivingpower forrotating the rollers II,I2 and I3. Dueto the combined action of I8, I9 and 29 androtary motion 2I forces the thinned wall IIwill' lengthen out and the originalwall25wil1 shorten. After a-few sec onds a suitable length of. thinned wallI! will havebeen obtained andthe-axial force l 9 is then removed; therollers, are backed off, the drill.

press stopped, and the finished workpiece I removed from mandrel 5.. Thefinished work pie e in this instance, as shown in Figure 3, consistsoftwo endsections I6 and 25 of .032 inch wall thickness joinedintegrallyby a section I'Lof tubing having a very much thinner wall, all threesec-.

tions having an inside diameter of .032 inch corresponding substantiallyto the outside diameter of mandrel 5. With reasonable care tosecureconcentricity of mandrel 5 and rollers II, I2 and I3 about the axisofmandrel 5, wallthicknesses of less than 1.001 inch arereadilyobtainable.

This corresponds to a reduction of over thirty to one in a single pass.a In spite of the-.foil-like nature of 'the thinned down" section, thecom-- pleted part will be relativelywrigid and strong mechanically. v

Figure 7 shows more in'detail the various steps set forth above indescribingour process, .but enlarged-so as to be more ;clearly;.-understood. The resulting'product is modified the, extent vthatgtheenclosing-end of the end section llihas 5-; been omitted so: thatthefinishedproduct isfan" open tubehavin'g thick end ferrules 'joined'by a 'havior of the me h P h! irom under punch 'relati velf'reducedintinieaitftmn wa'u portion,lbut all thre 'elportidns. have, the samein- (7 described iiia'yfbe better uh- I 'ng n i'sq e ldetailflthe :be-

tal'in theiregio'noi plastic 'flow during the carrying out of theproces's.

An elemental form of ourldcal extrusion; with Pr ss d a. ited f-rb ii aelworkl material, isillustrated -in figure. 6. In thief-instance a narrowwork blank I is supported ';py a-hacking member 40 andrestrained-lateralhi, except on s ide.;,in ,a suitableholder Also thatpressure deyelopedbya punch 42 is localized to substani l r her si n .43andfihafi ii i l tblew A he. pu c 4i isi' l q i nt' th work blank I thismoving away, or elongationof theregion- 16 takes place much morereadily,v after the punch a has progressed an' appreciable distancethrough rthe-wall oi the work Jolank; Infact -twhen the r punch42=-first enters or penetrates the work blank" the; material of region I6 is momentarily 2,efiectivelyconstrained from movingrby theten- -Vsion;i n. the work material locatedunder punch ,4Z".@:=,so:thata projectionor bump 44; isiormedsaid bump being shown exaggerated --i'or-.purposesof illustration. As thepunchpenetrates more deeplyintothematerial;elongation-thereof takes place more readily;i; I

. From this simpleexplanation of local extrusion it will lbeappreciated; that z-thefitotal'jrequi-red :forceiis considerably lessthan if itiwere neceslsaryto subject all. of the unworkdmaterialof9.312196 area blank .izoti'theunitpressure required asinvthecase.ofconventional-extrusion methods. ,c-.:App1yingtliis elementalprincipami local extriusion tothe' forms ofrapparatus describedheretofore, attention-is-zdirected ztoFigures 7 and -8.

The-beads I 5 or the" sexieral zrollers H, 12 and I3 function: in the.same mannen as the punch 42 and exert local: pressurempon-r the smallwork region-13. .As these rollers progressover the. work'blank il' due"to'rotation of the latter; compressive "stresses are builtxup' in'region'fl which :are 'sufilcient" to 9 cause-"plastic i flow of theinaterial comprising said: region; Becauseof the thick-unworked adjacentportion 2 5 of the work blank I g and the axial attachment thereof tothe mandrel 5, restraints ars I provided 3 which limit thflow ofmaterialinthe plane 'ofrotation. The efiectiveness oithese res'traints ismateriallyzassistd by making"- the radius brine rollers'darge comparedwith the radius of the bead I5. Figure '6 shows in aim-exaggerated firmthe corresponding operatieni performed upo'ri- Wdrk region. 43,

except that-thepunch '42 mnctionsamanr'ier p Cited that the geometericaishap or the region 'is not': symmetrical in any war neitii" does it areriess or a preciablyshirt position anau or rieh rid lieline'45 (seeFigural?) joiningi thefrol'le and mandrel axes; That is tosay; thisasymmetrical region 43 is not a specific 'portion ofwork material; butis actually a geometric volume which progressively moves with'theroller' through differentportions of a the work; blank during theextrusion operation. vFin -thers thee-surface of each rollerin-contactiwithitheworkregion 43 is one of the, components which.constitute -an ina feature more fully developed elsewhere herein."

I, the material: pgthe blank i'lowscut 1 42.; andpushesregion; I 6 away,v to-the right in Fig. 6. It'should benotedthat the 35665 .FEY that ti)Rica]. flfr IlaIS beIl. M

' portaiit feature er rorcs co'ri'tihubfufslyprogressing "hasis directedtol the fifeature l or applying,

erm a le? sequence" s that e tion 46 of each of th successive? andcomments I ileli the entire periphfans :comple'tely :bounded' extrusionaperture, which -is ergssqure iiitrical' regiofi is not a specifi thisasy "B i ifiir ll ermit m1 of the s'eq"efitl "scans j' the part cular iwork l V6 this local asymm'emeai a's'sociatdixtfudir'ifi aperture in Beaiisedt'o progressive? sean" ciireii iiiernt lljy. asziany atfial of theworfi'lilanli" 6onwe; was l T163? force (see arrow IO -shown inl ig cs3and 7)" is irl'additioii us and simuitaiieouswitii the alcove marinas.It is also 'sible ts compute all three" of theab'cve -mum ny perpradicals] motions"- simultaneously I if desired as long 'asthes'cannin gpath of thasy-m- P metrical geometrical volume --is -a reg-ular honrepeating paththroughthe werltigblarikr The scann ingpathgenerated in; Eigs= 1%, 7 and 8 --may be said to be essentiallyhelical in forth, as shewn in Figure-9,; with a rather fine pitch" -41due to -the relatively high peripheral speed of rotatiori Mas-comparedwith theaxial speed49 ofadvancement ofthe work. V Wehave found that thepitch should Joe sufiiciently fine as to pern iit-ari overlapping ofthelocal -portions durin'adjacent scans. The actu'al pitch used -11 dependsupon the kind and thickness of the blank material, the radius. of therollers, the radius of beads formed thereon, and the thickness andsurface finish required. However, the pitch between adjacent sections ofthe scanning path the arrangement shown, a rapid reciprocatory motion ofthe car 50 relative to -the blank 53 may v be provided by the crank 56and connecting rod 51, which motion is the equivalent of the rota-'tional motion' of Figs. 'l3. The compressive force 58 is at rightangles to the'reci'procating motion, and may be applied by any externalmeans (not shown). Suitable means, which may be of a conventional form,would berequired to slowly move the blank 53' ina third directionparallel to the surface of the blan'kand perpendicular to 'both thereciprocating motion and the force 58. The scanning pattern {generatedby the rapid reciprocating motion and the third motion will be zig-zag,and the pitch thereof need not be constant across the' width of thescanned area, i. e., it may be'coarsegfollowed by a relatively finepitchso as to produce a variable pitch scanning pattern. In any event, thescanning cycles should overlapto producethe proper scanning eifectfeatured by the invention.

From the. foregoing it will be understood by those skilled in the artthat the plastic flow produced by the passage of the geometric .volumeof material undergoing scanning at a given'time will develop a crystalpattern different from anything produced by conventional extrusionmethods; further, this pattern will be characteristic of our scanningextrusion methodso that from an examination of microphotographs,especially,

of the thinner portions of the finished product, it will be possible toidentify'the process from plastic flow lines or patterns which resultfrom practicing the scanning operation herein disclosed. Therefore, byan examination of the finished product it can be determined whether ornot the product was made by practicingour invention, i. e. by extrusionscanning. This flow pattern will naturally be influenced by the kind 7That is to say, our extrusion'pro'cess develops an identifiable crystalpattern which is charac-' teristic of scanning a localized volume ofwork at a given time, and by following a continuous path, etc. Theidentifying characteristics of the crystal pattern developed by ourextrusion scani may be attributed to such factors as the spiralformation characteristic of the scanning operation and apparatusemployed, the plastic flow resulting from scanning a'localizedgeometlines individualf'to. theproce blank: Consequently, the'tdtalforces I are much" much' lower than' would be' required ric volumewhich. imparts characteristic flow 1y, we feel entitled tocla-irn ainherently having novel features hat pr'aymot "be obvious: from a-c'asualfinspe'c priftheriofrbnt nevertheless are-only generated y the-*for71 extrusion scanning c'ontempla In the present disclosure, use the termgreat reduction asappliedtq-theresultirfg wall thickness o e and" maamese g ti the sense that very substantial elongat n ofthe Work blank isobtained by inasingle passi pf i It is a well known fact -inthe' artormetal drawing that a -considerably grater elongation is possiblewithout fracturefif the material is subjected to compressive stresses atright angles to the elongating tensile stres ses; arid' we have foundthat unusually' great tensile elongations without fracture may; be madeto irar piaee in a single pass through our extrusie'nepper tus evenformod'er'ate reduction 'bf wall thickness.

. This is'true because the rgion 24' (Figures"- 3 and 7 is subjected tosuch right angleic'ornpressive stresses. Furthermoreithe forg es weapply are concentrated 'to adimited l geometric volume as saidforce'sscan'through thework 'equ'i'red by conventional drawing operations forthe' same This will be more fully appreciated by reference to Figure 10,which is an enlarged-and somewhat modified view of' Figure 3;. Wher'ein"it is more clearly shown that th'e geometric extrusion volume 43 is notalwaysi bounded .on the mandrel side I by the mandrel surface: but 'maybe localized Withln'the metal of. the blank between the bead IBand'themandrel 5. "The metal within the geometric .volume .43 may. flow=plastically, Whilethe region 59i ofi'the'metaliibetweehi said volume 43and the mandrel Siiscausdtostretch axially in. tensile deformation; :However;1since hydrostaticepressure also .exists'; within the-region 59,the tensile elongationv characteristics of. the metal in this regionLaregreatly. enhanced with the result that tensile elongationsimay". beachieved which. are. greatly: in excessnof :those predictable byordinary tensile characteristics.

It should notbe overlooked,thattherearegtwo forms of elongation justdiscussed:'.(1);:Whereextrusion scanning takes place as, described withrespect to Figures '7 and-8,, producingiextremely great thinning andelongationvwithout;appreciable tensile elongation; and: (2)whererenhanced tensile elongation and extrusion; scanning a 1 combined 1as explained with; reference to Figure Althoughit will be seen that' thescanning aperture is loosely a partially 'bqundedz-port o of thematerial being, worked, thejentire periphery thereof is :effectivelyintegrated :to form a substantially continuous orifice.;' "It will jalso. be noted that the curvature of; the work blank where the scanningoperation'begins (see-Figureg'lin inordinatelyjfor very a1 therefore,there-is practically-inc-liinit"of ;thedegree of thinning attainable byour extrusion scanning .process.'. ThesefrequiredIdriving forces 1 are'always transmitted through the thickpnworke rtion of the blank sinceonlya single is "over'fthework is neces ry, Of course, it s ame. .befinderstood to be" impractical Ifo normail operaticfis'to'use'awdr 11am:initial Wrink1ih'g..}fThis"should "Ilfflafv silpp'oit'li'3, whlh i en Iw limitationbn'theadaptability'of our process for process, and whichintu'rni's mounted upon'a all types of extrusiom' but should serve tofursupporting base 154- whichlatter may be sealed the mantis. s

ther;-,distinguish,our process from conventional into; a ss r'neniber I-QIt is obvious to those spinn ,gdrawing and axi rolling operations 15skilled mtne art "that the intermediate thin where repeated passes ofthe work are necessary walled portion of the support '63 functions as afor accomplishing great reductions in wall thickheat isolating means forthe cathode 60. This ness. construction is a feature of a co-pendingappli- In practicing our invention, in place ofthe cation filed by usMay 12, 1948, Serial Number roller system described above for certaintypes 26,696, relating to a novel Vacuum Tube Conof work, it is possibleto use aroller-like tool struction.

10 (see Figure 11) which does not revolve on its It will be appreciatedthat by our method of axis. Such a tool has a rounded nose and wouldextrusion scanning, the scanning path per se simulate a primitive form01' [3001 used in spinmay take other forms, In a, form of scanning ning.However, we have found it is preferabl which is particularly applicablein making that the tool Ill be a roller which turns freely articles ofcone-shape by the present process, the on needle bearings. However, withthe simple scanning path takes the form of a flat spiral, with form ofro er 10 shOWn in the Portion the roller or other scanning toolprogressing H of the Work blank I eXielly ahead of the tool radiallyoutwardly on a rotating flat work blank.

is raised upon xcessively and curled back as As is apparent from theforegoing description,

t e t0 advanc s e a This is due t lack of our processis conservative involume of material,

the constraining effect on region 43 by the cylinand the inside diameterof the work blank may drical shoulder 45 of rollers H, H and I3 preberetained uniform throughout viously described. i It should be understoodthat it is not necessary A sim lar appearing curled beck portion is thatthe rollers, if designed to rotate, be driven shown xa r n Figure 10,but in this cas by friction from the work, but external driving y be eto excessive compression in region 43 means may be provided to rotatethe rollers with which causes region 43 to x n y nd and or relative tothe work being extruded.

ahead of the leadin d f the shoulder 46 Of Any suitable ductile materialmay be successroller l2. This excessive compression is brought 40 fullyd it process, including th bou y e t h tensile forces i r n metals whichare subject to brittle work harden- 59 restrict the free flow ofmaterial out of extruing under severe ld i w have used sion orifice 30.With the relatively great reduccopper, nickel, iron, tantah m,molybdenum, and tions normally d region 59 vanishes as does variousalloys, such as "Kovar and chrome-irons the above attendantobjectionable curl back. a t 1 1; t i ot t l may, of A form of toolconstruction mo e Sa f y course, be used, as well as those plastics orother h n those j described is shown in Figure materials which can beplastically deformed. It will be seen that a rod-like member 65 s p 7While the process as described utilizes round vided w th a rou ed ePesitiened symmetritubular sections over a smooth round mandrel eellyabout s 66, which nose is in forcible conand with external rollers, asan example, it is to be tact with work blank I to form e trusio epunderstood that this invention includes the ture 3U. Rotat o of the tooly be Provided adaptation where one or more rollers are mounted ifdesired in ord r t r pl e s i n fr as on the inside of the tubular workpiece and the in the case of a fixed roller by rolling f icti ne backingsurface consists of the inside wall of e p fi d in our roller sy d us aca hard cylinder surrounding the work piece.

ta t extruding Processes A hole 5 y b Various other modifications of theinvention used if des r to p y high pressure lubricant, may be made inits application to various types of and/or coolant to the region ne raperture devices but the ones described and/or suggested Furthermodifications of the rollers will sugmay be regarded as illustrative ofthe scope of the gest themselves to those skilled in the art. wh chinvention which is only limited by the prior art are considered to comewithin the scope of the and appended claims. present invention. Forexample, the nose or head h t i l i i of the tool may be provided withcircumferential 1, As an article of manufacture, a one piece p These psed not be ey e but tube of ductile conducting material having a relytake the m of m pl p als, With h atively thick portion and an extremelythin elonr s t work having r es 0r b p 0 its gated portion functioningas heat isolating means surface. for said thick portion, saidfirst-mentioned por- T backing mandrel member a fl tion being from 10 toseveral hundred times as wide variety of forms, and/or shapes asindicated thick as said elongated portion and the latter above. Thematerial for the rollers and backing between 0003 and 05 inch thicksurfaces should preferably be much harder than A cathode Support memberformed of 1101- the material being formed for obvious reasons. 10wcylindrical one piece body, having relatively W a found t y hard l steelsuitably thick end portions and an intermediate extremeground andpolished is satisfactory for cold-work- 1y thin elongated portion ofsubstantially less exing ordinary metals. Furthenthe use of preternaldiameter than that of theend portions, said ing relatively thick andanother of said sections 7 being elongated, extremely thin and foil likeand functioning as a. heat isolating means for said thick sectiomsaidelongated section being between .0003 and .005 inchQthick.v

L OYD P. GARNER. WILIJAM PARKER;

The fol REFERENCES crrED lowin'g refer ences are ofrecord in the file ofthis patent:

Number 11,009 507,572 691,540 10 1,199,080 1,596,751

15 Number UNITED STATES PATENTS Name Date Pratt June 6, 1854 Walsh Oct.31, 1893 g :Gieshoi dt Jan. 21, 1902 Jones Sept. 26, 1916 MillspaughAug. 17,1926 Peterson June 1, 1948 FOREIGN PATENTS Country Date- FranceJuly 20, 1914

